I love those vintage pink nylon circs! I have a couple of them!
My 16" US5 Susan Bates (white nylon) still has the original packaging!
My Boyes (pink nylon) are both 24", US 5 & US6.
You're quite right. They are very easy to use. The "join" is absent, and no snagging EVER! Ya hafta soak them in HOT water before using them, to relax those cords. But they respond well.
Ebay is selling them today. A whole batch of the Marcia Lynns for $7.99 if you want them NOW. The "bid" is $5.99 at the moment. They look just like my white nylon circs.
Here is a baby blue US6 Susan Bates nylon circfor sale on Ebay! $3.25
And here is a size US4! $3.25
You simply cannot beat the price, even with a little shipping!
Here are some white Susan Bates circs.
I typed VINTAGE CIRCULAR KNITTING NEEDLES in the eBAY search engine, and up popped slugs of old-timey circs. Very affordable priced, too.
You should be able to eventually get all the sizes and lengths you need. There must be a lot of old gals like me (and older) who are pushing off, and their children are giving all their mother's old circs to Good Will, etc. I think these Ebay vendors must search all the Thrift Stores for these old timey circs, etc.